1. Field of the Invention
This invention relates to a vertical engine of the type employed in outboard motors and more particularly to an improved fuel injection system for such vertical engines.
2. Description of the Related Art
The use of fuel injection for internal combustion engines in order to improve performance, particularly fuel economy and exhaust emission control, is well known. A wide variety of types of fuel injection systems have been proposed for this purpose. Many of these systems inject the fuel into the induction system rather than into the combustion chamber. Such so-called "manifold injected" engines have advantages over carbureted engines. However, there are a number of additional advantages that can be obtained by utilizing direct cylinder injection.
By using direct cylinder injection, it is possible to more accurately control the actual fuel-air ratio in the combustion chamber on each cycle of operation. In addition, by utilizing direct cylinder injection, it is possible to obtain stratification in the combustion chamber and thus operate with a lean mixture under some or most running conditions. That is, by stratifying the charge in the combustion chamber, it is not necessary to have a homogeneous stoichiometric charge in the entire combustion chamber. All that is required is to have a stoichiometric charge present in the vicinity of the spark plug at the time that it is fired in order for combustion to be initiated.
There are, however, a number of reasons why direct cylinder injection is not utilized more widely. Not the least of these is cost. Not only are the injectors more costly and more critical with direct injected engines, but the supply system for supplying fuel to the injectors also becomes more complicated and expensive.
When direct cylinder injection is employed, the injection pressures must not only be higher, but they also must be more accurately controlled. As a result of this, it has been the practice to normally employ reciprocating plunger-type pumps for direct injected engines. Such pumps have a number of components, are complex, and in fact, can become quite bulky.
Although these problems may be overcome in some applications, there is a desire to employ direct cylinder or high pressure fuel injection systems for outboard motors. Like other vehicle applications, outboard motors are subject to concern over environmental control and also fuel economy. In addition, outboard motors frequently utilize two-cycle engines as their power plants. These engines can benefit as much or more from direct cylinder fuel injection as four-cycle engines.
In addition to the cost factor, the complexity of high pressure injection systems makes it more difficult to integrate them into outboard motors. One reason for this is that the outboard motor is a very compact type of device, and it may be difficult to locate the necessary components for a high pressure fuel injection system. In addition, the injection pump normally is driven off of the engine crankshaft and is frequently in timed relationship thereto. This further complicates the placement and driving of such high pressure fuel injection pumps in outboard motors.
In addition to these problems, an outboard motor has another problem which is somewhat unique and different from automotive or other vehicle applications. That is, it is normally the practice to mount an outboard motor engine so that its crankshaft rotates about a vertically extending axis. As a result, the orientation of the engine is quite different than automotive and other applications. This further complicates the location and driving of accessories, such as high pressure fuel injection pumps.